This project will investigate the feasibility and the development of an implantable, compliant spine joint fixation prosthesis. The implant, different from existing rigid spine fixation devices which completely immobilize an unstable joint (for joint fusion and/or healing of fractured bone), will be designed to protect the spinal cord and nerve roots by assisting the joint and intervertebral disc in supporting and distributing loads while allowing for limited motion between vertebrae and surrounding joints. PHASE I of research will be directed at the completion and verification of a compliant carbon fiber composite implant via bench tests and human cadavera studies. Mekanika, Inc., is jointly pursuing the development of intraoperative instrumentation for quantitative assessment of spine joint instability pre and post decompressive surgery (a Spinal Stiffness Gauge [SSG]); the SSG is undergoing a clinical study at the University of Miami. The company's goal is that of a Spinal System employing both a means for diagnosing instability [SSG] and a means for treatment of instability with a compliant implant. An implant, required for any one spine joint, would be a function of the SSG stiffness measurement of the joint in compression, tension, and torsional tests. During PHASE II, an animal model (baboon) study will be completed, and a multi-centered clinical study initiated, to prove safety and efficacy of the treatment.